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Sema: refactor detection of comptime-known consts

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This was previously implemented by analyzing the AIR prior to the ZIR
`make_ptr_const` instruction. This solution was highly delicate, and in
particular broke down whenever there was a second `alloc` between the
`store` and `alloc` instructions, which is especially common in
destructure statements.

Sema now uses a different strategy to detect whether a `const` is
comptime-known. When the `alloc` is created, Sema begins tracking all
pointers and stores which refer to that allocation in temporary local
state. If any store is not comptime-known or has a higher runtime index
than the allocation, the allocation is marked as being runtime-known.
When we reach the `make_ptr_const` instruction, if the allocation is not
marked as runtime-known, it must be comptime-known. Sema will use the
set of `store` instructions to re-initialize the value in comptime
memory. We optimize for the common case of a single `store` instruction
by not creating a comptime alloc in this case, instead directly plucking
the result value from the instruction.

Resolves: #16083
This commit is contained in:
mlugg 2023-09-15 14:49:40 +01:00 • committed by Matthew Lugg
parent fc3ff26237
commit 644041b3a4
4 changed files with 489 additions and 170 deletions
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591
src/Sema.zig
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@ -111,6 +111,35 @@ prev_stack_alignment_src: ?LazySrcLoc = null,
/// the struct/enum/union type created should be placed. Otherwise, it is `.none`.
builtin_type_target_index: InternPool.Index = .none,
/// Links every pointer derived from a base `alloc` back to that `alloc`. Used
/// to detect comptime-known `const`s.
/// TODO: ZIR liveness analysis would allow us to remove elements from this map.
base_allocs: std.AutoHashMapUnmanaged(Air.Inst.Index, Air.Inst.Index) = .{},
/// Runtime `alloc`s are placed in this map to track all comptime-known writes
/// before the corresponding `make_ptr_const` instruction.
/// If any store to the alloc depends on a runtime condition or stores a runtime
/// value, the corresponding element in this map is erased, to indicate that the
/// alloc is not comptime-known.
/// If the alloc remains in this map when `make_ptr_const` is reached, its value
/// is comptime-known, and all stores to the pointer must be applied at comptime
/// to determine the comptime value.
/// Backed by gpa.
maybe_comptime_allocs: std.AutoHashMapUnmanaged(Air.Inst.Index, MaybeComptimeAlloc) = .{},
const MaybeComptimeAlloc = struct {
/// The runtime index of the `alloc` instruction.
runtime_index: Value.RuntimeIndex,
/// Backed by sema.arena. Tracks all comptime-known stores to this `alloc`. Due to
/// RLS, a single comptime-known allocation may have arbitrarily many stores.
/// This may also contain `set_union_tag` instructions.
stores: std.ArrayListUnmanaged(Air.Inst.Index) = .{},
/// Backed by sema.arena. Contains instructions such as `optional_payload_ptr_set`
/// which have side effects so will not be elided by Liveness: we must rewrite these
/// instructions to be nops instead of relying on Liveness.
non_elideable_pointers: std.ArrayListUnmanaged(Air.Inst.Index) = .{},
};
const std = @import("std");
const math = std.math;
const mem = std.mem;
@ -840,6 +869,8 @@ pub fn deinit(sema: *Sema) void {
sema.post_hoc_blocks.deinit(gpa);
}
sema.unresolved_inferred_allocs.deinit(gpa);
sema.base_allocs.deinit(gpa);
sema.maybe_comptime_allocs.deinit(gpa);
sema.* = undefined;
}
@ -2643,6 +2674,7 @@ fn zirCoerceResultPtr(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileE
.placeholder = Air.refToIndex(bitcasted_ptr).?,
});
try sema.checkKnownAllocPtr(ptr, bitcasted_ptr);
return bitcasted_ptr;
},
.inferred_alloc_comptime => {
@ -2690,7 +2722,9 @@ fn zirCoerceResultPtr(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileE
const dummy_ptr = try trash_block.addTy(.alloc, sema.typeOf(ptr));
const dummy_operand = try trash_block.addBitCast(pointee_ty, .void_value);
return sema.coerceResultPtr(block, src, ptr, dummy_ptr, dummy_operand, &trash_block);
const new_ptr = try sema.coerceResultPtr(block, src, ptr, dummy_ptr, dummy_operand, &trash_block);
try sema.checkKnownAllocPtr(ptr, new_ptr);
return new_ptr;
}
fn coerceResultPtr(
@ -3719,7 +3753,13 @@ fn zirAllocExtended(
.address_space = target_util.defaultAddressSpace(target, .local),
},
});
return block.addTy(.alloc, ptr_type);
const ptr = try block.addTy(.alloc, ptr_type);
if (small.is_const) {
const ptr_inst = Air.refToIndex(ptr).?;
try sema.maybe_comptime_allocs.put(gpa, ptr_inst, .{ .runtime_index = block.runtime_index });
try sema.base_allocs.put(gpa, ptr_inst, ptr_inst);
}
return ptr;
}
const result_index = try block.addInstAsIndex(.{
@ -3730,6 +3770,10 @@ fn zirAllocExtended(
} },
});
try sema.unresolved_inferred_allocs.putNoClobber(gpa, result_index, .{});
if (small.is_const) {
try sema.maybe_comptime_allocs.put(gpa, result_index, .{ .runtime_index = block.runtime_index });
try sema.base_allocs.put(gpa, result_index, result_index);
}
return Air.indexToRef(result_index);
}
@ -3748,60 +3792,26 @@ fn zirMakePtrConst(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileErro
const inst_data = sema.code.instructions.items(.data)[inst].un_node;
const alloc = try sema.resolveInst(inst_data.operand);
const alloc_ty = sema.typeOf(alloc);
var ptr_info = alloc_ty.ptrInfo(mod);
const ptr_info = alloc_ty.ptrInfo(mod);
const elem_ty = ptr_info.child.toType();
// Detect if all stores to an `.alloc` were comptime-known.
ct: {
var search_index: usize = block.instructions.items.len;
const air_tags = sema.air_instructions.items(.tag);
const air_datas = sema.air_instructions.items(.data);
const store_inst = while (true) {
if (search_index == 0) break :ct;
search_index -= 1;
const candidate = block.instructions.items[search_index];
switch (air_tags[candidate]) {
.dbg_stmt, .dbg_block_begin, .dbg_block_end => continue,
.store, .store_safe => break candidate,
else => break :ct,
}
};
while (true) {
if (search_index == 0) break :ct;
search_index -= 1;
const candidate = block.instructions.items[search_index];
switch (air_tags[candidate]) {
.dbg_stmt, .dbg_block_begin, .dbg_block_end => continue,
.alloc => {
if (Air.indexToRef(candidate) != alloc) break :ct;
break;
},
else => break :ct,
}
}
const store_op = air_datas[store_inst].bin_op;
const store_val = (try sema.resolveMaybeUndefVal(store_op.rhs)) orelse break :ct;
if (store_op.lhs != alloc) break :ct;
// Remove all the unnecessary runtime instructions.
block.instructions.shrinkRetainingCapacity(search_index);
if (try sema.resolveComptimeKnownAllocValue(block, alloc, null)) |val| {
var anon_decl = try block.startAnonDecl();
defer anon_decl.deinit();
return sema.analyzeDeclRef(try anon_decl.finish(elem_ty, store_val, ptr_info.flags.alignment));
const new_mut_ptr = try sema.analyzeDeclRef(try anon_decl.finish(elem_ty, val.toValue(), ptr_info.flags.alignment));
return sema.makePtrConst(block, new_mut_ptr);
}
// If this is already a comptime-mutable allocation, we don't want to emit an error - the stores
// If this is already a comptime-known allocation, we don't want to emit an error - the stores
// were already performed at comptime! Just make the pointer constant as normal.
implicit_ct: {
const ptr_val = try sema.resolveMaybeUndefVal(alloc) orelse break :implicit_ct;
if (ptr_val.isComptimeMutablePtr(mod)) break :implicit_ct;
if (!ptr_val.isComptimeMutablePtr(mod)) {
// It could still be a constant pointer to a decl
const decl_index = ptr_val.pointerDecl(mod) orelse break :implicit_ct;
const decl_val = mod.declPtr(decl_index).val.toIntern();
if (mod.intern_pool.isRuntimeValue(decl_val)) break :implicit_ct;
}
return sema.makePtrConst(block, alloc);
}
@ -3812,9 +3822,234 @@ fn zirMakePtrConst(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileErro
return sema.fail(block, init_src, "value with comptime-only type '{}' depends on runtime control flow", .{elem_ty.fmt(mod)});
}
// This is a runtime value.
return sema.makePtrConst(block, alloc);
}
/// If `alloc` is an inferred allocation, `resolved_inferred_ty` is taken to be its resolved
/// type. Otherwise, it may be `null`, and the type will be inferred from `alloc`.
fn resolveComptimeKnownAllocValue(sema: *Sema, block: *Block, alloc: Air.Inst.Ref, resolved_alloc_ty: ?Type) CompileError!?InternPool.Index {
const mod = sema.mod;
const alloc_ty = resolved_alloc_ty orelse sema.typeOf(alloc);
const ptr_info = alloc_ty.ptrInfo(mod);
const elem_ty = ptr_info.child.toType();
const alloc_inst = Air.refToIndex(alloc) orelse return null;
const comptime_info = sema.maybe_comptime_allocs.fetchRemove(alloc_inst) orelse return null;
const stores = comptime_info.value.stores.items;
// Since the entry existed in `maybe_comptime_allocs`, the allocation is comptime-known.
// We will resolve and return its value.
// We expect to have emitted at least one store, unless the elem type is OPV.
if (stores.len == 0) {
const val = (try sema.typeHasOnePossibleValue(elem_ty)).?.toIntern();
return sema.finishResolveComptimeKnownAllocValue(val, alloc_inst, comptime_info.value);
}
// In general, we want to create a comptime alloc of the correct type and
// apply the stores to that alloc in order. However, before going to all
// that effort, let's optimize for the common case of a single store.
simple: {
if (stores.len != 1) break :simple;
const store_inst = stores[0];
const store_data = sema.air_instructions.items(.data)[store_inst].bin_op;
if (store_data.lhs != alloc) break :simple;
const val = Air.refToInterned(store_data.rhs).?;
assert(mod.intern_pool.typeOf(val) == elem_ty.toIntern());
return sema.finishResolveComptimeKnownAllocValue(val, alloc_inst, comptime_info.value);
}
// The simple strategy failed: we must create a mutable comptime alloc and
// perform all of the runtime store operations at comptime.
var anon_decl = try block.startAnonDecl();
defer anon_decl.deinit();
const decl_index = try anon_decl.finish(elem_ty, try mod.undefValue(elem_ty), ptr_info.flags.alignment);
const decl_ptr = try mod.intern(.{ .ptr = .{
.ty = alloc_ty.toIntern(),
.addr = .{ .mut_decl = .{
.decl = decl_index,
.runtime_index = block.runtime_index,
} },
} });
// Maps from pointers into the runtime allocs, to comptime-mutable pointers into the mut decl.
var ptr_mapping = std.AutoHashMap(Air.Inst.Index, InternPool.Index).init(sema.arena);
try ptr_mapping.ensureTotalCapacity(@intCast(stores.len));
ptr_mapping.putAssumeCapacity(alloc_inst, decl_ptr);
var to_map = try std.ArrayList(Air.Inst.Index).initCapacity(sema.arena, stores.len);
for (stores) |store_inst| {
const bin_op = sema.air_instructions.items(.data)[store_inst].bin_op;
to_map.appendAssumeCapacity(Air.refToIndex(bin_op.lhs).?);
}
const tmp_air = sema.getTmpAir();
while (to_map.popOrNull()) |air_ptr| {
if (ptr_mapping.contains(air_ptr)) continue;
const PointerMethod = union(enum) {
same_addr,
opt_payload,
eu_payload,
field: u32,
elem: u64,
};
const inst_tag = tmp_air.instructions.items(.tag)[air_ptr];
const air_parent_ptr: Air.Inst.Ref, const method: PointerMethod = switch (inst_tag) {
.struct_field_ptr => blk: {
const data = tmp_air.extraData(
Air.StructField,
tmp_air.instructions.items(.data)[air_ptr].ty_pl.payload,
).data;
break :blk .{
data.struct_operand,
.{ .field = data.field_index },
};
},
.struct_field_ptr_index_0,
.struct_field_ptr_index_1,
.struct_field_ptr_index_2,
.struct_field_ptr_index_3,
=> .{
tmp_air.instructions.items(.data)[air_ptr].ty_op.operand,
.{ .field = switch (inst_tag) {
.struct_field_ptr_index_0 => 0,
.struct_field_ptr_index_1 => 1,
.struct_field_ptr_index_2 => 2,
.struct_field_ptr_index_3 => 3,
else => unreachable,
} },
},
.ptr_slice_ptr_ptr => .{
tmp_air.instructions.items(.data)[air_ptr].ty_op.operand,
.{ .field = Value.slice_ptr_index },
},
.ptr_slice_len_ptr => .{
tmp_air.instructions.items(.data)[air_ptr].ty_op.operand,
.{ .field = Value.slice_len_index },
},
.ptr_elem_ptr => blk: {
const data = tmp_air.extraData(
Air.Bin,
tmp_air.instructions.items(.data)[air_ptr].ty_pl.payload,
).data;
const idx_val = (try sema.resolveMaybeUndefVal(data.rhs)).?;
break :blk .{
data.lhs,
.{ .elem = idx_val.toUnsignedInt(mod) },
};
},
.bitcast => .{
tmp_air.instructions.items(.data)[air_ptr].ty_op.operand,
.same_addr,
},
.optional_payload_ptr_set => .{
tmp_air.instructions.items(.data)[air_ptr].ty_op.operand,
.opt_payload,
},
.errunion_payload_ptr_set => .{
tmp_air.instructions.items(.data)[air_ptr].ty_op.operand,
.eu_payload,
},
else => unreachable,
};
const decl_parent_ptr = ptr_mapping.get(Air.refToIndex(air_parent_ptr).?) orelse {
// Resolve the parent pointer first.
// Note that we add in what seems like the wrong order, because we're popping from the end of this array.
try to_map.appendSlice(&.{ air_ptr, Air.refToIndex(air_parent_ptr).? });
continue;
};
const new_ptr_ty = tmp_air.typeOfIndex(air_ptr, &mod.intern_pool).toIntern();
const new_ptr = switch (method) {
.same_addr => try mod.intern_pool.getCoerced(sema.gpa, decl_parent_ptr, new_ptr_ty),
.opt_payload => try mod.intern(.{ .ptr = .{
.ty = new_ptr_ty,
.addr = .{ .opt_payload = decl_parent_ptr },
} }),
.eu_payload => try mod.intern(.{ .ptr = .{
.ty = new_ptr_ty,
.addr = .{ .eu_payload = decl_parent_ptr },
} }),
.field => |field_idx| try mod.intern(.{ .ptr = .{
.ty = new_ptr_ty,
.addr = .{ .field = .{
.base = decl_parent_ptr,
.index = field_idx,
} },
} }),
.elem => |elem_idx| (try decl_parent_ptr.toValue().elemPtr(new_ptr_ty.toType(), @intCast(elem_idx), mod)).toIntern(),
};
try ptr_mapping.put(air_ptr, new_ptr);
}
// We have a correlation between AIR pointers and decl pointers. Perform all stores at comptime.
for (stores) |store_inst| {
switch (sema.air_instructions.items(.tag)[store_inst]) {
.set_union_tag => {
// If this tag has an OPV payload, there won't be a corresponding
// store instruction, so we must set the union payload now.
const bin_op = sema.air_instructions.items(.data)[store_inst].bin_op;
const air_ptr_inst = Air.refToIndex(bin_op.lhs).?;
const tag_val = (try sema.resolveMaybeUndefVal(bin_op.rhs)).?;
const union_ty = sema.typeOf(bin_op.lhs).childType(mod);
const payload_ty = union_ty.unionFieldType(tag_val, mod);
if (try sema.typeHasOnePossibleValue(payload_ty)) |payload_val| {
const new_ptr = ptr_mapping.get(air_ptr_inst).?;
const store_val = try mod.unionValue(union_ty, tag_val, payload_val);
try sema.storePtrVal(block, .unneeded, new_ptr.toValue(), store_val, union_ty);
}
},
.store, .store_safe => {
const bin_op = sema.air_instructions.items(.data)[store_inst].bin_op;
const air_ptr_inst = Air.refToIndex(bin_op.lhs).?;
const store_val = (try sema.resolveMaybeUndefVal(bin_op.rhs)).?;
const new_ptr = ptr_mapping.get(air_ptr_inst).?;
try sema.storePtrVal(block, .unneeded, new_ptr.toValue(), store_val, mod.intern_pool.typeOf(store_val.toIntern()).toType());
},
else => unreachable,
}
}
// The value is finalized - load it!
const val = (try sema.pointerDeref(block, .unneeded, decl_ptr.toValue(), alloc_ty)).?.toIntern();
return sema.finishResolveComptimeKnownAllocValue(val, alloc_inst, comptime_info.value);
}
/// Given the resolved comptime-known value, rewrites the dead AIR to not
/// create a runtime stack allocation.
/// Same return type as `resolveComptimeKnownAllocValue` so we can tail call.
fn finishResolveComptimeKnownAllocValue(sema: *Sema, result_val: InternPool.Index, alloc_inst: Air.Inst.Index, comptime_info: MaybeComptimeAlloc) CompileError!?InternPool.Index {
// We're almost done - we have the resolved comptime value. We just need to
// eliminate the now-dead runtime instructions.
// We will rewrite the AIR to eliminate the alloc and all stores to it.
// This will cause instructions deriving field pointers etc of the alloc to
// become invalid, however, since we are removing all stores to those pointers,
// they will be eliminated by Liveness before they reach codegen.
// The specifics of this instruction aren't really important: we just want
// Liveness to elide it.
const nop_inst: Air.Inst = .{ .tag = .bitcast, .data = .{ .ty_op = .{ .ty = .u8_type, .operand = .zero_u8 } } };
sema.air_instructions.set(alloc_inst, nop_inst);
for (comptime_info.stores.items) |store_inst| {
sema.air_instructions.set(store_inst, nop_inst);
}
for (comptime_info.non_elideable_pointers.items) |ptr_inst| {
sema.air_instructions.set(ptr_inst, nop_inst);
}
return result_val;
}
fn makePtrConst(sema: *Sema, block: *Block, alloc: Air.Inst.Ref) CompileError!Air.Inst.Ref {
const mod = sema.mod;
const alloc_ty = sema.typeOf(alloc);
@ -3868,7 +4103,11 @@ fn zirAlloc(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.I
.flags = .{ .address_space = target_util.defaultAddressSpace(target, .local) },
});
try sema.queueFullTypeResolution(var_ty);
return block.addTy(.alloc, ptr_type);
const ptr = try block.addTy(.alloc, ptr_type);
const ptr_inst = Air.refToIndex(ptr).?;
try sema.maybe_comptime_allocs.put(sema.gpa, ptr_inst, .{ .runtime_index = block.runtime_index });
try sema.base_allocs.put(sema.gpa, ptr_inst, ptr_inst);
return ptr;
}
fn zirAllocMut(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.Inst.Ref {
@ -3925,6 +4164,8 @@ fn zirAllocInferred(
} },
});
try sema.unresolved_inferred_allocs.putNoClobber(gpa, result_index, .{});
try sema.maybe_comptime_allocs.put(gpa, result_index, .{ .runtime_index = block.runtime_index });
try sema.base_allocs.put(sema.gpa, result_index, result_index);
return Air.indexToRef(result_index);
}
@ -3992,91 +4233,15 @@ fn zirResolveInferredAlloc(sema: *Sema, block: *Block, inst: Zir.Inst.Index) Com
if (!ia1.is_const) {
try sema.validateVarType(block, ty_src, final_elem_ty, false);
} else ct: {
// Detect if the value is comptime-known. In such case, the
// last 3 AIR instructions of the block will look like this:
//
// %a = inferred_alloc
// %b = bitcast(%a)
// %c = store(%b, %d)
//
// If `%d` is comptime-known, then we want to store the value
// inside an anonymous Decl and then erase these three AIR
// instructions from the block, replacing the inst_map entry
// corresponding to the ZIR alloc instruction with a constant
// decl_ref pointing at our new Decl.
// dbg_stmt instructions may be interspersed into this pattern
// which must be ignored.
if (block.instructions.items.len < 3) break :ct;
var search_index: usize = block.instructions.items.len;
const air_tags = sema.air_instructions.items(.tag);
const air_datas = sema.air_instructions.items(.data);
const store_inst = while (true) {
if (search_index == 0) break :ct;
search_index -= 1;
const candidate = block.instructions.items[search_index];
switch (air_tags[candidate]) {
.dbg_stmt, .dbg_block_begin, .dbg_block_end => continue,
.store, .store_safe => break candidate,
else => break :ct,
}
};
const bitcast_inst = while (true) {
if (search_index == 0) break :ct;
search_index -= 1;
const candidate = block.instructions.items[search_index];
switch (air_tags[candidate]) {
.dbg_stmt, .dbg_block_begin, .dbg_block_end => continue,
.bitcast => break candidate,
else => break :ct,
}
};
while (true) {
if (search_index == 0) break :ct;
search_index -= 1;
const candidate = block.instructions.items[search_index];
if (candidate == ptr_inst) break;
switch (air_tags[candidate]) {
.dbg_stmt, .dbg_block_begin, .dbg_block_end => continue,
else => break :ct,
}
}
const store_op = air_datas[store_inst].bin_op;
const store_val = (try sema.resolveMaybeUndefVal(store_op.rhs)) orelse break :ct;
if (store_op.lhs != Air.indexToRef(bitcast_inst)) break :ct;
if (air_datas[bitcast_inst].ty_op.operand != ptr) break :ct;
const new_decl_index = d: {
var anon_decl = try block.startAnonDecl();
defer anon_decl.deinit();
const new_decl_index = try anon_decl.finish(final_elem_ty, store_val, ia1.alignment);
break :d new_decl_index;
};
try mod.declareDeclDependency(sema.owner_decl_index, new_decl_index);
// Remove the instruction from the block so that codegen does not see it.
block.instructions.shrinkRetainingCapacity(search_index);
try sema.maybeQueueFuncBodyAnalysis(new_decl_index);
if (std.debug.runtime_safety) {
// The inferred_alloc should never be referenced again
sema.air_instructions.set(ptr_inst, .{ .tag = undefined, .data = undefined });
}
const interned = try mod.intern(.{ .ptr = .{
.ty = final_ptr_ty.toIntern(),
.addr = .{ .decl = new_decl_index },
} });
} else if (try sema.resolveComptimeKnownAllocValue(block, ptr, final_ptr_ty)) |val| {
var anon_decl = try block.startAnonDecl();
defer anon_decl.deinit();
const new_decl_index = try anon_decl.finish(final_elem_ty, val.toValue(), ia1.alignment);
const new_mut_ptr = Air.refToInterned(try sema.analyzeDeclRef(new_decl_index)).?.toValue();
const new_const_ptr = (try mod.getCoerced(new_mut_ptr, final_ptr_ty)).toIntern();
// Remap the ZIR oeprand to the resolved pointer value
sema.inst_map.putAssumeCapacity(Zir.refToIndex(inst_data.operand).?, Air.internedToRef(interned));
sema.inst_map.putAssumeCapacity(Zir.refToIndex(inst_data.operand).?, Air.internedToRef(new_const_ptr));
// Unless the block is comptime, `alloc_inferred` always produces
// a runtime constant. The final inferred type needs to be
@ -4199,6 +4364,7 @@ fn zirArrayBasePtr(
.Array, .Vector => return base_ptr,
.Struct => if (elem_ty.isTuple(mod)) {
// TODO validate element count
try sema.checkKnownAllocPtr(start_ptr, base_ptr);
return base_ptr;
},
else => {},
@ -4225,7 +4391,10 @@ fn zirFieldBasePtr(
const elem_ty = sema.typeOf(base_ptr).childType(mod);
switch (elem_ty.zigTypeTag(mod)) {
.Struct, .Union => return base_ptr,
.Struct, .Union => {
try sema.checkKnownAllocPtr(start_ptr, base_ptr);
return base_ptr;
},
else => {},
}
return sema.failWithStructInitNotSupported(block, src, sema.typeOf(start_ptr).childType(mod));
@ -4636,7 +4805,8 @@ fn validateUnionInit(
}
const new_tag = Air.internedToRef(tag_val.toIntern());
_ = try block.addBinOp(.set_union_tag, union_ptr, new_tag);
const set_tag_inst = try block.addBinOp(.set_union_tag, union_ptr, new_tag);
try sema.checkComptimeKnownStore(block, set_tag_inst);
}
fn validateStructInit(
@ -4939,6 +5109,7 @@ fn validateStructInit(
try sema.tupleFieldPtr(block, init_src, struct_ptr, field_src, @intCast(i), true)
else
try sema.structFieldPtrByIndex(block, init_src, struct_ptr, @intCast(i), field_src, struct_ty, true);
try sema.checkKnownAllocPtr(struct_ptr, default_field_ptr);
const init = Air.internedToRef(field_values[i]);
try sema.storePtr2(block, init_src, default_field_ptr, init_src, init, field_src, .store);
}
@ -5366,6 +5537,7 @@ fn storeToInferredAlloc(
// Create a store instruction as a placeholder. This will be replaced by a
// proper store sequence once we know the stored type.
const dummy_store = try block.addBinOp(.store, ptr, operand);
try sema.checkComptimeKnownStore(block, dummy_store);
// Add the stored instruction to the set we will use to resolve peer types
// for the inferred allocation.
try inferred_alloc.prongs.append(sema.arena, .{
@ -8663,7 +8835,8 @@ fn analyzeOptionalPayloadPtr(
// If the pointer resulting from this function was stored at comptime,
// the optional non-null bit would be set that way. But in this case,
// we need to emit a runtime instruction to do it.
_ = try block.addTyOp(.optional_payload_ptr_set, child_pointer, optional_ptr);
const opt_payload_ptr = try block.addTyOp(.optional_payload_ptr_set, child_pointer, optional_ptr);
try sema.checkKnownAllocPtr(optional_ptr, opt_payload_ptr);
}
return Air.internedToRef((try mod.intern(.{ .ptr = .{
.ty = child_pointer.toIntern(),
@ -8687,11 +8860,14 @@ fn analyzeOptionalPayloadPtr(
const is_non_null = try block.addUnOp(.is_non_null_ptr, optional_ptr);
try sema.addSafetyCheck(block, src, is_non_null, .unwrap_null);
}
const air_tag: Air.Inst.Tag = if (initializing)
.optional_payload_ptr_set
else
.optional_payload_ptr;
return block.addTyOp(air_tag, child_pointer, optional_ptr);
if (initializing) {
const opt_payload_ptr = try block.addTyOp(.optional_payload_ptr_set, child_pointer, optional_ptr);
try sema.checkKnownAllocPtr(optional_ptr, opt_payload_ptr);
return opt_payload_ptr;
} else {
return block.addTyOp(.optional_payload_ptr, child_pointer, optional_ptr);
}
}
/// Value in, value out.
@ -8851,7 +9027,8 @@ fn analyzeErrUnionPayloadPtr(
// the error union error code would be set that way. But in this case,
// we need to emit a runtime instruction to do it.
try sema.requireRuntimeBlock(block, src, null);
_ = try block.addTyOp(.errunion_payload_ptr_set, operand_pointer_ty, operand);
const eu_payload_ptr = try block.addTyOp(.errunion_payload_ptr_set, operand_pointer_ty, operand);
try sema.checkKnownAllocPtr(operand, eu_payload_ptr);
}
return Air.internedToRef((try mod.intern(.{ .ptr = .{
.ty = operand_pointer_ty.toIntern(),
@ -8878,11 +9055,13 @@ fn analyzeErrUnionPayloadPtr(
try sema.panicUnwrapError(block, src, operand, .unwrap_errunion_err_ptr, .is_non_err_ptr);
}
const air_tag: Air.Inst.Tag = if (initializing)
.errunion_payload_ptr_set
else
.unwrap_errunion_payload_ptr;
return block.addTyOp(air_tag, operand_pointer_ty, operand);
if (initializing) {
const eu_payload_ptr = try block.addTyOp(.errunion_payload_ptr_set, operand_pointer_ty, operand);
try sema.checkKnownAllocPtr(operand, eu_payload_ptr);
return eu_payload_ptr;
} else {
return block.addTyOp(.unwrap_errunion_payload_ptr, operand_pointer_ty, operand);
}
}
/// Value in, value out
@ -22048,6 +22227,7 @@ fn ptrCastFull(
});
} else {
assert(dest_ptr_ty.eql(dest_ty, mod));
try sema.checkKnownAllocPtr(operand, result_ptr);
return result_ptr;
}
}
@ -22075,7 +22255,9 @@ fn zirPtrCastNoDest(sema: *Sema, block: *Block, extended: Zir.Inst.Extended.Inst
}
try sema.requireRuntimeBlock(block, src, null);
return block.addBitCast(dest_ty, operand);
const new_ptr = try block.addBitCast(dest_ty, operand);
try sema.checkKnownAllocPtr(operand, new_ptr);
return new_ptr;
}
fn zirTruncate(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.Inst.Ref {
@ -26161,7 +26343,9 @@ fn fieldPtr(
}
try sema.requireRuntimeBlock(block, src, null);
return block.addTyOp(.ptr_slice_ptr_ptr, result_ty, inner_ptr);
const field_ptr = try block.addTyOp(.ptr_slice_ptr_ptr, result_ty, inner_ptr);
try sema.checkKnownAllocPtr(inner_ptr, field_ptr);
return field_ptr;
} else if (ip.stringEqlSlice(field_name, "len")) {
const result_ty = try sema.ptrType(.{
.child = .usize_type,
@ -26183,7 +26367,9 @@ fn fieldPtr(
}
try sema.requireRuntimeBlock(block, src, null);
return block.addTyOp(.ptr_slice_len_ptr, result_ty, inner_ptr);
const field_ptr = try block.addTyOp(.ptr_slice_len_ptr, result_ty, inner_ptr);
try sema.checkKnownAllocPtr(inner_ptr, field_ptr);
return field_ptr;
} else {
return sema.fail(
block,
@ -26295,14 +26481,18 @@ fn fieldPtr(
try sema.analyzeLoad(block, src, object_ptr, object_ptr_src)
else
object_ptr;
return sema.structFieldPtr(block, src, inner_ptr, field_name, field_name_src, inner_ty, initializing);
const field_ptr = try sema.structFieldPtr(block, src, inner_ptr, field_name, field_name_src, inner_ty, initializing);
try sema.checkKnownAllocPtr(inner_ptr, field_ptr);
return field_ptr;
},
.Union => {
const inner_ptr = if (is_pointer_to)
try sema.analyzeLoad(block, src, object_ptr, object_ptr_src)
else
object_ptr;
return sema.unionFieldPtr(block, src, inner_ptr, field_name, field_name_src, inner_ty, initializing);
const field_ptr = try sema.unionFieldPtr(block, src, inner_ptr, field_name, field_name_src, inner_ty, initializing);
try sema.checkKnownAllocPtr(inner_ptr, field_ptr);
return field_ptr;
},
else => {},
}
@ -27066,21 +27256,24 @@ fn elemPtr(
};
try checkIndexable(sema, block, src, indexable_ty);
switch (indexable_ty.zigTypeTag(mod)) {
.Array, .Vector => return sema.elemPtrArray(block, src, indexable_ptr_src, indexable_ptr, elem_index_src, elem_index, init, oob_safety),
.Struct => {
const elem_ptr = switch (indexable_ty.zigTypeTag(mod)) {
.Array, .Vector => try sema.elemPtrArray(block, src, indexable_ptr_src, indexable_ptr, elem_index_src, elem_index, init, oob_safety),
.Struct => blk: {
// Tuple field access.
const index_val = try sema.resolveConstValue(block, elem_index_src, elem_index, .{
.needed_comptime_reason = "tuple field access index must be comptime-known",
});
const index: u32 = @intCast(index_val.toUnsignedInt(mod));
return sema.tupleFieldPtr(block, src, indexable_ptr, elem_index_src, index, init);
break :blk try sema.tupleFieldPtr(block, src, indexable_ptr, elem_index_src, index, init);
},
else => {
const indexable = try sema.analyzeLoad(block, indexable_ptr_src, indexable_ptr, indexable_ptr_src);
return elemPtrOneLayerOnly(sema, block, src, indexable, elem_index, elem_index_src, init, oob_safety);
},
}
};
try sema.checkKnownAllocPtr(indexable_ptr, elem_ptr);
return elem_ptr;
}
/// Asserts that the type of indexable is pointer.
@ -27120,20 +27313,20 @@ fn elemPtrOneLayerOnly(
},
.One => {
const child_ty = indexable_ty.childType(mod);
switch (child_ty.zigTypeTag(mod)) {
.Array, .Vector => {
return sema.elemPtrArray(block, src, indexable_src, indexable, elem_index_src, elem_index, init, oob_safety);
},
.Struct => {
const elem_ptr = switch (child_ty.zigTypeTag(mod)) {
.Array, .Vector => try sema.elemPtrArray(block, src, indexable_src, indexable, elem_index_src, elem_index, init, oob_safety),
.Struct => blk: {
assert(child_ty.isTuple(mod));
const index_val = try sema.resolveConstValue(block, elem_index_src, elem_index, .{
.needed_comptime_reason = "tuple field access index must be comptime-known",
});
const index: u32 = @intCast(index_val.toUnsignedInt(mod));
return sema.tupleFieldPtr(block, indexable_src, indexable, elem_index_src, index, false);
break :blk try sema.tupleFieldPtr(block, indexable_src, indexable, elem_index_src, index, false);
},
else => unreachable, // Guaranteed by checkIndexable
}
};
try sema.checkKnownAllocPtr(indexable, elem_ptr);
return elem_ptr;
},
}
}
@ -27660,7 +27853,9 @@ fn coerceExtra(
return sema.coerceInMemory(val, dest_ty);
}
try sema.requireRuntimeBlock(block, inst_src, null);
return block.addBitCast(dest_ty, inst);
const new_val = try block.addBitCast(dest_ty, inst);
try sema.checkKnownAllocPtr(inst, new_val);
return new_val;
}
switch (dest_ty.zigTypeTag(mod)) {
@ -29379,8 +29574,9 @@ fn storePtr2(
// We do this after the possible comptime store above, for the case of field_ptr stores
// to unions because we want the comptime tag to be set, even if the field type is void.
if ((try sema.typeHasOnePossibleValue(elem_ty)) != null)
if ((try sema.typeHasOnePossibleValue(elem_ty)) != null) {
return;
}
if (air_tag == .bitcast) {
// `air_tag == .bitcast` is used as a special case for `zirCoerceResultPtr`
@ -29415,10 +29611,65 @@ fn storePtr2(
});
}
if (is_ret) {
_ = try block.addBinOp(.store, ptr, operand);
} else {
_ = try block.addBinOp(air_tag, ptr, operand);
const store_inst = if (is_ret)
try block.addBinOp(.store, ptr, operand)
else
try block.addBinOp(air_tag, ptr, operand);
try sema.checkComptimeKnownStore(block, store_inst);
return;
}
/// Given an AIR store instruction, checks whether we are performing a
/// comptime-known store to a local alloc, and updates `maybe_comptime_allocs`
/// accordingly.
fn checkComptimeKnownStore(sema: *Sema, block: *Block, store_inst_ref: Air.Inst.Ref) !void {
const store_inst = Air.refToIndex(store_inst_ref).?;
const inst_data = sema.air_instructions.items(.data)[store_inst].bin_op;
const ptr = Air.refToIndex(inst_data.lhs) orelse return;
const operand = inst_data.rhs;
const maybe_base_alloc = sema.base_allocs.get(ptr) orelse return;
const maybe_comptime_alloc = sema.maybe_comptime_allocs.getPtr(maybe_base_alloc) orelse return;
ct: {
if (null == try sema.resolveMaybeUndefVal(operand)) break :ct;
if (maybe_comptime_alloc.runtime_index != block.runtime_index) break :ct;
return maybe_comptime_alloc.stores.append(sema.arena, store_inst);
}
// Store is runtime-known
_ = sema.maybe_comptime_allocs.remove(maybe_base_alloc);
}
/// Given an AIR instruction transforming a pointer (struct_field_ptr,
/// ptr_elem_ptr, bitcast, etc), checks whether the base pointer refers to a
/// local alloc, and updates `base_allocs` accordingly.
fn checkKnownAllocPtr(sema: *Sema, base_ptr: Air.Inst.Ref, new_ptr: Air.Inst.Ref) !void {
const base_ptr_inst = Air.refToIndex(base_ptr) orelse return;
const new_ptr_inst = Air.refToIndex(new_ptr) orelse return;
const alloc_inst = sema.base_allocs.get(base_ptr_inst) orelse return;
try sema.base_allocs.put(sema.gpa, new_ptr_inst, alloc_inst);
switch (sema.air_instructions.items(.tag)[new_ptr_inst]) {
.optional_payload_ptr_set, .errunion_payload_ptr_set => {
const maybe_comptime_alloc = sema.maybe_comptime_allocs.getPtr(alloc_inst) orelse return;
try maybe_comptime_alloc.non_elideable_pointers.append(sema.arena, new_ptr_inst);
},
.ptr_elem_ptr => {
const tmp_air = sema.getTmpAir();
const pl_idx = tmp_air.instructions.items(.data)[new_ptr_inst].ty_pl.payload;
const bin = tmp_air.extraData(Air.Bin, pl_idx).data;
const index_ref = bin.rhs;
// If the index value is runtime-known, this pointer is also runtime-known, so
// we must in turn make the alloc value runtime-known.
if (null == try sema.resolveMaybeUndefVal(index_ref)) {
_ = sema.maybe_comptime_allocs.remove(alloc_inst);
}
},
else => {},
}
}
@ -30517,7 +30768,9 @@ fn coerceCompatiblePtrs(
} else is_non_zero;
try sema.addSafetyCheck(block, inst_src, ok, .cast_to_null);
}
return sema.bitCast(block, dest_ty, inst, inst_src, null);
const new_ptr = try sema.bitCast(block, dest_ty, inst, inst_src, null);
try sema.checkKnownAllocPtr(inst, new_ptr);
return new_ptr;
}
fn coerceEnumToUnion(

10
src/Zir.zig
View file

@ -941,8 +941,16 @@ pub const Inst = struct {
/// Allocates stack local memory.
/// Uses the `un_node` union field. The operand is the type of the allocated object.
/// The node source location points to a var decl node.
/// A `make_ptr_const` instruction should be used once the value has
/// been stored to the allocation. To ensure comptime value detection
/// functions, there are some restrictions on how this pointer should be
/// used prior to the `make_ptr_const` instruction: no pointer derived
/// from this `alloc` may be returned from a block or stored to another
/// address. In other words, it must be trivial to determine whether any
/// given pointer derives from this one.
alloc,
/// Same as `alloc` except mutable.
/// Same as `alloc` except mutable. As such, `make_ptr_const` need not be used,
/// and there are no restrictions on the usage of the pointer.
alloc_mut,
/// Allocates comptime-mutable memory.
/// Uses the `un_node` union field. The operand is the type of the allocated object.

40
test/behavior/destructure.zig
View file

@ -98,3 +98,43 @@ test "destructure from struct init with named tuple fields" {
try expect(y == 200);
try expect(z == 300);
}
test "destructure of comptime-known tuple is comptime-known" {
const x, const y = .{ 1, 2 };
comptime assert(@TypeOf(x) == comptime_int);
comptime assert(x == 1);
comptime assert(@TypeOf(y) == comptime_int);
comptime assert(y == 2);
}
test "destructure of comptime-known tuple where some destinations are runtime-known is comptime-known" {
var z: u32 = undefined;
var x: u8, const y, z = .{ 1, 2, 3 };
comptime assert(@TypeOf(y) == comptime_int);
comptime assert(y == 2);
try expect(x == 1);
try expect(z == 3);
}
test "destructure of tuple with comptime fields results in some comptime-known values" {
var runtime: u32 = 42;
const a, const b, const c, const d = .{ 123, runtime, 456, runtime };
// a, c are comptime-known
// b, d are runtime-known
comptime assert(@TypeOf(a) == comptime_int);
comptime assert(@TypeOf(b) == u32);
comptime assert(@TypeOf(c) == comptime_int);
comptime assert(@TypeOf(d) == u32);
comptime assert(a == 123);
comptime assert(c == 456);
try expect(b == 42);
try expect(d == 42);
}

18
test/behavior/eval.zig
View file

@ -1724,3 +1724,21 @@ comptime {
assert(foo[1] == 2);
assert(foo[2] == 0x55);
}
test "const with allocation before result is comptime-known" {
const x = blk: {
const y = [1]u32{2};
_ = y;
break :blk [1]u32{42};
};
comptime assert(@TypeOf(x) == [1]u32);
comptime assert(x[0] == 42);
}
test "const with specified type initialized with typed array is comptime-known" {
const x: [3]u16 = [3]u16{ 1, 2, 3 };
comptime assert(@TypeOf(x) == [3]u16);
comptime assert(x[0] == 1);
comptime assert(x[1] == 2);
comptime assert(x[2] == 3);
}